A pest around the world
How did house sparrows become a pest? With the spread of agriculture and urbanization sparrows have become one of the abundant groups of birds in the world. Most sparrow species are closely linked with humans and spread with people as humans moved out of Africa and throughout the world. Perhaps the most successful sparrow, and the one we all know about, is the house sparrow, who can be found on every continent in the world save frigid Antarctica. Throughout time, as their abundance has fluctuated so has public opinion about these resilient little birds. Today we will look at the story of sparrows around the world, and how public perceptions and management has changed over time.
As humans moved out of Africa and into Europe, so did our sparrow friends. Being mostly seed eaters, sparrow ancestors were migratory. But the development of agriculture gave sparrows a consistent source of food year round. Like us, they settled, nesting in the buildings we built and eating the crops we produced. During the 1700’s there was an explosion in the European sparrow population as human settlements spread further and agriculture continued to focus on cereal grains such as wheat and oats, an ideal food source for sparrows.
By the mid 1700’s there was a superabundance of sparrows throughout Central Europe, with some written accounts describing flocks of sparrows so large that they blocked out the sun. These enormous flocks of sparrows could decimate important crop yields at a time when cereal grains made up a substantial portion of crops grown in Europe, making the sparrow a worthy foe. To combat this problem, many local governments established a bounty in which sparrow heads could be turned in to the government for tax credits. By the end of World War II, the first observable declines in the European sparrow population were seen. This change is likely due to a decrease in horse manure, more efficient grain harvesting technology, and poultry no longer being fed in the open. It is difficult to know whether the management strategies implemented by governments have led to a continued decline in house sparrow numbers or whether changes agricultural practices have played a bigger role. Ironically, in many European countries today house sparrows are now a protected species as their numbers have declined so much. There are now campaigns in the United Kingdom to save the house sparrow!
One of the most interesting stories of sparrow control comes from China, during the reign of Mao Zedong and “The Great Leap Forward”. Mao considered the Eurasian tree sparrow (a close relative of the house sparrow) one of the “four great pests” to the nation because of their abundance and negative impact on grain crop yields. In March of 1958 Mao declared war on tree sparrows, and people all over the country went outside banging pots and pans together, waving flags, destroying nests, and killing nestlings with guns and slingshots.
At first, the effort appeared to be a remarkable success as crop yields initially improved. But before long, locust and grasshopper populations, freed from sparrow predation, exploded and decimated the grain crops. The crop damage from the insects lead to a famine in which more than 35 million Chinese people died. In a desperate attempt to stop the destruction, the government began importing sparrows from the Soviet Union. Following this disaster, Mao quickly protected tree sparrows and added bedbugs to his lest of four pests instead. This example illustrates the severe damage that can be inflicted when sweeping changes are made to an ecosystem.
What can we learn from these failures in providing effective management of pest species? In both the European and Chinese stories, the problem came from a basic misunderstanding of how sparrows function in an ecosystem. Prior to the European sparrow population explosion of the 1700’s, written accounts show that some were already advocating for control of sparrows by destroying nests and eggs. But it wasn’t until the population exploded and started decimating crops that any action was taken. In China’s case, the government thought that tree sparrows strictly fed on seeds, and it wasn’t until after the sparrow population had been destroyed that they found research showing that tree sparrows also can control insect populations because they do feed on insects during breeding season.
The sparrows in China and Europe were a native species, but house sparrows were purposely introduced from Great Britain to the United States in the 1850’s as a form of pest control. 50 years after their introduction, house sparrows had spread virtually across the entire country and are almost universally regarded as pests. Instead of providing pest control, house sparrows are competing with our native bluebirds, and this all stemmed from a lack of understanding of the species.
These stories highlight the importance of incorporating good science into management strategies for wildlife. With your help on the Sparrow Swap Project, we will be able to improve our understanding of how different management strategies impact house sparrows and native birds, which will hopefully ultimately lead to better management decisions in the future. By participating, you are providing data and increasing knowledge that will be instrumental in providing effective management for our native songbirds.
If you would like to learn more about the “4 pests campaign in China, check out this article!
If you are interested in reading more about the story of sparrows in general, check out tthis article written by NC State Professor Rob Dunn!
This post was written by Dominic Eannarino, a recent graduate from NC State. You can learn more about Dominic and the rest of the Sparrow Swap Team on our team page.